An unusual thermophilic bacterium has been isolated from deep subsurface sediments and tested for its ability to enhance Fe(III), Co(III), and Cr(VI) reduction. Without the bacterium, abiotic metal reduction was insignificant at temperatures below 45 degrees C, but became a major process at 75 degrees C. Addition of the bacterium enhanced the reduction of these metals up to fourfold, probably by nonspecific mechanisms. This study demonstrates abiotic and biotic metal reduction under organic-rich thermic conditions, and suggests that thermally and/or biologically enhanced metal reduction may provide an alternative for remediating metal contamination.